1. Field of the Invention
This invention relates to improvements in corona charging devices.
2. Description of the Prior Art
In systems requiring a plurality of corona chargers, such as in electrostatographic copiers and/or printers, it is traditional to provide a power supply for each charger. A significant reduction in system cost could be realized if one power supply could be used to drive all the corona chargers.
Corona discharge is sensitive to atmospheric conditions of pressure and humidity because changes in atmospheric conditions alter the mobility of the charge carriers in air. If a corona wire is maintained at a constant potential, current from the corona wire will change with changing atmospheric conditions. Therefore, corona charger power supplies are by necessity constant average current supplies to compensate for the atmospheric condition sensitivity of the corona system.
However, constant current sources do not lead themselves to multiple-charger systems having only a single power supply because each charger would be sensitive to the operation of the other chargers. For example, if one charger wire were to break, a constant current power supply would increase its output potential to compensate for the drop in total supply current. This would cause excessive wire vibration, elevated current output, and possible arcing conditions in the other chargers.